Floating cover for a tank

ABSTRACT

In a floating cover for inside a tank a plurality of spaced parallel support bars extend across the tops of laterally spaced horizontal pontoons that support them. Metal sheets covering the spaces between the bars have edge portions resting on the bars and clamped against them by clamping bars to form a deck. The deck may be provided with vertical sleeves, in which posts of different lengths can be mounted for spacing the deck different distances from the bottom of a tank.

United States Patent 119 Nelson 1 Jan. 21, 1975 [54] FLOATING COVER FORA TANK 3,493,143 2/1970: Thompson et al 220/26 S Inventor: Arden H-Nelson 34 Thom 3,587,911 6/1971 Cretth 220/26 S S ickl ,P 15143 ew ey aPrimary Examiner-William 1. Price Filed! [186- 1972 AssistantExaminerStephen Marcus [211 App]. No 317 371 Attorney, Agent, orFirm-Brown, Murray, Flick & v

Peckham [52] US. Cl. 220/221,220/26 R 51 Int. Cl B656 87/18 [57]ABSTRACT [58] Field of Search.....-220/26 R, 26 D, 26 E, 26 S, ln afloating cover for inside a tank a plurality of 220/26 SA; 4/ 172.12spaced parallel support bars extend across the tops of laterally spacedhorizontal pontoons' that. support [56] References Cited them. Metalsheets covering the spaces between the UNITED STATES PATENTS bars haveedge portions resting on the bars and clamped against them by clampingbars to form a 220/26 S deck. The deck may be provided with verticalsleeves, 8/1937 Dickman in which posts of different lengths can bemounted for 2,563,016 8/1951 Feild 220/26 R p g the deck differentdistances from the bottom 3,104,775 9/1963 Champagnat 220/26 S of atank. 3,319,329 5/1967 Knutsen et al 220/26 S I 3,409,165 11/1968 Creith220/26 R 10 Claims, 10 Drawmg Flgures t 1'4 Fl T- -T- w H ll! 1!! 1 ll..T ll? ll 5/ 11 46 n 11 /4 11 11 4, 2 1 r t 50 35 .44 43 4 52 7 1 l ,F

PATENTED JAN 21 I975 SHEEI 10F 5 rll I) II BUT 1 (W U T 4 1 a m UT L IHHYHMH H .m m HUnnq w x2 H H QUW I Nik PAIENTED JAN 2] I975 3.861555 saw20F 5 SHEET 3 [IF 5 PATENTEI] JANZI I975 PATENnnmm I975 saw u or sFLOATING COVER FOR A TANK It is common practice to provide tankscontaining volatile liquids with internal floating covers that rise andfall in the tanks in accordance with the depth of the liquid therein.These covers reduce or eliminate the air space above the liquid andthereby control evaporation which otherwise would cause loss of aconsiderable amount of the liquid and also would cause air pollution. Italso is not uncommon to mount vertical posts in such a cover forlimiting the distance that it can move downwardly in a tank so that thecover will not touch the equipment beneath it in the tank when theliquid level is low. When it is desired to clean out the bottom of thetank, it may be necessary for the cover to be at a higher level toprovide enough room beneath it for workmen. This has been accomplishedby adjusting the posts downwardly through the cover to increase theirlength below it. However, in order to have posts long enough to do this,they normally extend a considerable distance above the cover, wherebythey limit the distance the cover can rise in the tank and hence thecapacity of the tank, because the posts will engage the roof of thetank. Also, in floating covers known heretofore, organic sealingmaterials have been used between the edges of the metal panels formingthe covers which also have required a great many holes for fasteners.These seals have not stood up well under the chemical reaction caused bythe liquids and vapors in the tanks. The sealants usually deteriorate intwo or three years of service and thus reduce the efficiency of thecovers.

It is among the objects of this invention to provide an internalfloating tank cover which has an extra strong pontoon-supported deckthat does not require organic sealants, which has permanently tightjoints, which does not require openings through the metal sheets formingthe deck for fasteners to hold the sheets in place, which can risesubstantially the full height of a tank, which can move laterally in atank and also accommodate itself to tanks that are out of round, whichstops nearly all loss of liquid contents of the tank by evaporation, andin which the pontoons are easily attached to the deck and can be readilyshifted laterally relative to the deck.

The preferred embodiment of the invention is illustrated in theaccompanying drawings, in which FIG. 1 is a plan view of the cover in atank shown in section;

FIG. 2 is an elevation and central vertical section of the tank showingthe floating cover diagrammatically in its lowest position and in dottedlines at a higher elevation;

FIG. 3 is an enlarged cross section of a pontoon showing how it isattached to the overlying deck;

FIG. 4 is a fragmentary side view. of the pontoon, with the deck insection above it;

FIG. 5 is an enlarged fragmentary plan view of the cover, with partsbroken away;

FIG. 6 is an enlarged fragmentary vertical section through an edgeportion of the cover;

FIG. 7 is an enlarged fragmentary vertical section through the centralportion of the cover;

FIG. 8 is an enlarged fragmentary vertical section taken on the lineVIII-VIII of FIG. 1;

FIG. 9 is a vertical section taken on the line IXIX- of FIG. 8; and

FIG. 10 is an enlarged fragmentary cross section of modified clampingand support bars.

Referring to FIGS. 1, 2 and 5 of the drawings, a circular tank 1 isshown in which there is a floating cover. The cover has a continuousflat deck supported by spaced parallel floatation members or pontoons 2that can float on liquid in the tank. Preferably, the pontoons aretubular members with their ends sealed by brackets, each of which ischannel shaped, with a vertical web 3 welded to the end of a pontoontube 4 and with outwardly projecting upper and lower flanges 5.

The pontoons are held in their proper positions by spaced parallelsupport bars extending across their tops. As shown in FIGS. 3 and 4,each of these bars 7 is provided with an upwardly opening channel 8 thatextends lengthwise of the bar. The bottom of each bar has laterallyprojecting side flanges 9, the upper surfaces of which are engaged bythe inturned upper ends of U-shaped clips 10 that hang down from thebars. Screwed into the bottoms of these clips are screws 11 that extendthrough the out-turned ends of metal clamping strips 12 extending aroundthe bottom of tubes 4 to hold the bars and pontoons tightly together. Itwill be seen that by loosening the screws, the pontoons can be movedlaterally along the support bars to any desired position. This isadvantageous when it is found necessary to move a pontoon in this mannerin order to avoid some obstruction below it in the tank. Also, byloosening the screws, the support bars and clamping strips 12 can beadjusted lengthwise along the pontoons to provide the correct distancebetween the bars.

Covering the spaces between support bars 7 are thin metal sheets 14,preferably aluminum, that extend the full length of the bars with theiredge portions resting on the bars. These sheets are rigidly connected toeach bar by means of a clamping bar 15 in channel 8 of the support bar.The clamping bar engages the upper surfaces of the edge portions of thesheets. Vertical bolts 16 extend down through the clamping bar, betweenthe underlying sheets and through the support bar in order to clamp theedge portions of the sheets against the walls of the channel to hold thebars and sheets tightly together. Preferably, as shown in FIG. 4, theside walls of the channel are provided with steps 17 extendinglengthwise of the bars, and the clamping bar is shaped to overlie thesteps and also extend down between them. Consequently, the edge portionsof the sheets are bent down over the steps in the channel to hold themtightly in place and also to form seals without the use of gaskets orother sealing material. The metal-to-metal seals are permanent andadequate for sealing against any pressure drop across the floatingcover. Gas leakage associated with covers that use adhesives andcaulking compounds is eliminated.

The metal sheets 14 extend outwardly beyond the support bars and overliea horizontal rim plate 20, from the outer edge of which a vertical rimplate 21 extends downwardly to a level near the level of the bottom ofthe pontoons as shown in FIGS. 2, 5 and 6. This vertical rim plate isattached by brackets 22 (FIGS. 1 and 5) to the ends of short tubularpontoons 23 located between the ends of the main pontoons. As shown inFIG. 6, the horizontal rim plate 20 is attached to the bottom of themetal sheets by means of bolts 25 extending down through short splicebars 26 that overlie the sheets and the ends of the clamping and supportbars, to which the splice bars-are attached by bolts 27. The verticalrim plate extends downwardly far enough to penetrate the liquid in thetank beneath the cover so that gas cannot escape around the lower edge.

To form a sliding seal between the circular deck and the side of thesurrounding tank, a molded flexible sealing member 30 is clamped to'theedge of the deck by clamping bars 31 and bolts 32. The flexible sealnormally is inclined upwardly away from the rim plates, with its outeredge portion engaging the side of the tank. The seal also engageshorizontal rim plate around the edges of the metal sheets. Since theseal attempts to assume a position having less inclination than shown,it will remain in engagement with the tank even though the tank is outof round or the closed cover shifts horizontally. The seal also exerts apowerful selfcentering action on the cover.

Since there is generally at least a central column 34 in such a tank,and sometimes many columns, the center of the cover or any other placewhere columns will be is'provided with an opening lined with a verticalwall member 35 surrounding the column and spaced from it as shown inFIGS. 1, 2 and 7. Secured to the top of the wall member is a flat plate36, the opening through which is somewhat larger than the column so thatit will not engage the column. However, to prevent escape of volatilesup through that opening, a pair of superimposed flexible sealing rings37 are mounted on the plate and snugly engage the column. As wall member35 can slide across the bottomof plate 36, the seal does not interferewith lateral movement of the cover. When the cover rises in the tank,plate 36 pushes the sealing rings up the column. When the cover descendsin the tank, the sealing rings will slide down the column by gravityunless they happen to stick at some point, in which case they are pulleddown by a pair of normally slack metal cables 38 connecting plate 36with the underlying wall member. These cables also electrically groundthe plate to the rest of the cover.

Each of the long pontoons is formed from a plurality of the tubes 4disposed in alignment with their ends spaced apart as shown in FIG. 9.The adjacent ends of these tubes are closed by the vertical webs 41 ofbrackets that have parallel upper and lower flanges 42. The flanges ofone bracket overlap those of the adjoining bracket. These overlappingflanges are provided with aligned vertical openings registering with anopening in the deck above them. Extending through all of these openingsis a vertical slepve 43 that is held in place by a collar 44 welded toit and tightly secured by bolts 45 to the deck and upper bracket flanges42. The sleeve holds the brackets together and also prevents adjoiningbrackets from tilting relative to each other. A threaded cap 46 on theupper end of the sleeve holds a flanged post 47 in place in the sleeve.The post extends a predetermined distance, such as 3% feet, below thedeck. When it is desired to clean out the tank the posts can be removedfrom the upper ends of the sleeves while the cover is still floating ata relatively high level in the tank, and longer posts can be substitutedfor them, after which the caps are replaced. Thereafter, when the tankis emptied the long posts will engage the bottom of the tank and holdthe deck at a higher level than it ordinarily is held by the shorterposts when the tank is empty or nearly so. It it is not desired to everchange posts, the sleeves 43 and caps 46 can be omitted, and posts withclosed upper ends rigidly mounted in the space between the brackets bybolting them directly to the brackets.

The flanges 5 of the brackets on the ends of the pontoons likewise areprovided with vertically aligned openings, and the horizontal rim plateand the metal sheets above it are provided with similar openingsregistering with those below. As shown in FIG. 5, sleeves 50 are rigidlymounted in these openings. The upper ends of the sleeves are threadedand provided with screw caps 51 (FIG. 1) that hold removable posts 52(FIG. 5) in place.

The manner in which the metal panels 14 are clamped to the support barsresults in the deck developing the full percent strength of the panels.This means that the entire deck performs as if it were made from asingle large sheet of aluminum.

With the lower ends of the post-receiving sleeves below the liquidlevel, vapors cannot escape up through them even when their cas areremoved for changing posts.

A modification of the sheet-supporting and clamping bars is shown inFIG. 10, although the holding and sealing principle is the same aspreviously described. That is, the edge portions of the sheets are bentor deformed when the clamping and support bars are clamped together,whereby the sheets are held securely and permanent metal-to-metal sealsare formed. Thus, a support bar 55 is provided in its upper surface witha pair of laterally spaced grooves 56 extending lengthwise of the bar,and a clamping bar 57 above it is provided with parallel ribs 58 thatwill fit into the grooves. The edge portions of deck sheets 59 are laidon the support bar and then the clamping bar is drawn down tightlyagainst the sheets by bolts 60. This causes the ribs to deform thesheets into the grooves, which tightly holds the sheets and also formsseals to prevent escape of gas around the edges of the sheets.

According to the provisions of the patent statutes, I have explained theprinciple of my invention and have illustrated and described what I nowconsider to represent its best embodiment. However, I desire to have itunderstood that, within the scope of the appended claims, the'inventionmaybe practiced otherwise than as specifically illustrated anddescribed.

I claim:

1. A floating cover for inside a tank, comprising a plurality oflaterally spaced horizontal tubular pontoons, a plurality of spacedparallel support bars extending across the tops of the pontoons andsupported thereby, metal sheets covering the spaces between the bars andhaving edge portions resting on the bars, said sheets being spaced abovethe pontoons and extending across them, clamping bars engaging the uppersurfaces of said edge portions of the sheets, vertical fastenersextending through the clamping and support bars for holding them tightlytogether to clamp the edge portions of the sheets between them to form adeck above the pontoons, and sealing means extending around said deckfor sliding engagement with the side wall of a tank.

2. A floating cover according to claim 1, in which each support bar andthe overlying clamping bar are provided with interengaging ribs andgrooves extending lengthwise thereof with said edge portions of thesheets pressed into the grooves by said ribs.-

3. A floating cover according to claim 1, in which the bottom of eachsupport bar is provided with laterally projecting side flanges, saidcover including hanger members engaging the upper surfaces of saidflanges and hanging down below the support bars above the pontoons, ndclamping bands extending up around each pontoon and fastened to saidhanger members above it to connect said support bars and pontoonstogether,

4. A floating cover according to claim 1, in which the bottom of eachsupport bar is provided with laterally projecting side flanges, saidcover including clips engaging the upper surfaces of said flanges andhanging down below the support bars, the clips being disposed in a pairof parallel rows above each pontoon, and clamping bands extending uparound each pontoon with each band fastened to a pair of said clips inthe two rows above the pontoon for connecting said support bars andpontoons together.

5. A floating cover according to claim 4, in which each of said clips isof general U-shape with its upper ends turned toward each other andslidable along said support bar flanges, the bottom of each clip havinga hole through it, the cover including a bolt extending through eachclip hole and the adjoining clamping band to hold them together.

6. A floating cover according to claim 1, in which each of said supportbars is provided with an upwardly opening channel extending lengthwisethereof and receiving the edge portions of adjoining sheets, and eachclamping bar extends down into one'of the channels and clamps the edgeportions of the sheets therein against the inside of the channel.

7. A floating cover according to claim 6, .in which the sidewalls ofsaid channels are provided with steps extending lengthwise thereof, andsaid clamping bars are shaped to overlie said steps and also extend downbetween them, whereby said clamped edge portions of the metal sheets arevent between the adjoining clamping and support bars.

8. A floating cover according to claim 1, in which at least some of saidpontoons include longitudinally spaced aligned tubular members, a pairof brackets secured to the opposed ends of adjacent tubular members,each bracket having upper and lower horizontal flanges disposed inoverlapping relation with the flanges of the other bracket, said flangesand the metal sheet above them having aligned vertical openingstherethrough, and a vertical sleeve mounted in said openings andprojecting above said sheet and below the brackets, said cover includinga post extending through each sleeve and downwardly below it, and aremovable cap mounted on the upper end of the sleeve, said post beingremovable upwardly through the sleeve when said cap is removed, wherebythe post can be replaced by a post of a different length.

9. A floating cover according to claim 8, including a collar secured tosaid sleeve abovesaid deck, and fasteners extending down through thecollar and underlying metal sheet and upper flanges of said brackets forconnecting them rigidly together.

10. A floating cover for inside a tank, comprising a plurality oflaterally spaced horizontal pontoons, a deck supported by the pontoons,at least some of said pontoons including longitudinally spaced alignedtubular members, a pair of brackets secured to the opposed ends ofadjacent tubular members, each bracket having upper and lower horizontalflanges disposed in overlap ping relation with the flanges of the otherbracket, said flanges and deck having aligned vertical openingstherethrough, and a vertical sleeve mounted in said openings andprojecting above the deck and below-the brackets, said cover alsoincluding a post extending through each sleeve and downwardly belowit,and a removable cap mounted on the upper end of the sleeve,

placed by a post of a different length.

1. A floating cover for inside a tank, comprising a plurality oflaterally spaced horizontal tubular pontoons, a plurality of spacedparallel support bars extending across the tops of the pontoons andsupported thereby, metal sheets covering the spaces between the bars andhaving edge portions resting on the bars, said sheets being spaced abovethe pontoons and extending across them, clamping bars engaging the uppersurfaces of said edge portions of the sheets, vertical fastenersextending through the clamping and support bars for holding them tightlytogether to clamp the edge portions of the sheets between them to form adeck above the pontoons, and sealing means extending around said deckfor sliding engagement with the side wall of a tank.
 2. A floating coveraccording to claim 1, in which each support bar and the overlyingclamping bar are provided with interengaging ribs and grooves extendinglengthwise thereof with said edge portions of the sheets pressed intothe grooves by said ribs.
 3. A floating cover according to claim 1, inwhich the bottom of each support bar is provided with laterallyprojecting side flanges, said cover including hanger members engagingthe upper surfaces of said flanges and hanging down below the supportbars above the pontoons, nd clamping bands extending up around eachpontoon and fastened to said hanger members above it to connect saidsupport bars and pontoons together.
 4. A floating cover according toclaim 1, in which the bottom of each support bar is provided withlaterally projecting side flanges, said cover including clips engagingthe upper surfaces of said flanges and hanging down below the supportbars, the clips being disposed in a pair of parallel rows above eachpontoon, and clamping bands extending up around each pontoon with eachband fastened to a pair of said clips in the two rows above the pontoonfor connecting said support bars and pontoons together.
 5. A floatingcover according to claim 4, in which each of said clips is of generalU-shape with its upper ends turned toward each other and slidable alongsaid support bar flanges, the bottom of each clip having a hole throughit, the cover incLuding a bolt extending through each clip hole and theadjoining clamping band to hold them together.
 6. A floating coveraccording to claim 1, in which each of said support bars is providedwith an upwardly opening channel extending lengthwise thereof andreceiving the edge portions of adjoining sheets, and each clamping barextends down into one of the channels and clamps the edge portions ofthe sheets therein against the inside of the channel.
 7. A floatingcover according to claim 6, in which the side walls of said channels areprovided with steps extending lengthwise thereof, and said clamping barsare shaped to overlie said steps and also extend down between them,whereby said clamped edge portions of the metal sheets are vent betweenthe adjoining clamping and support bars.
 8. A floating cover accordingto claim 1, in which at least some of said pontoons includelongitudinally spaced aligned tubular members, a pair of bracketssecured to the opposed ends of adjacent tubular members, each brackethaving upper and lower horizontal flanges disposed in overlappingrelation with the flanges of the other bracket, said flanges and themetal sheet above them having aligned vertical openings therethrough,and a vertical sleeve mounted in said openings and projecting above saidsheet and below the brackets, said cover including a post extendingthrough each sleeve and downwardly below it, and a removable cap mountedon the upper end of the sleeve, said post being removable upwardlythrough the sleeve when said cap is removed, whereby the post can bereplaced by a post of a different length.
 9. A floating cover accordingto claim 8, including a collar secured to said sleeve above said deck,and fasteners extending down through the collar and underlying metalsheet and upper flanges of said brackets for connecting them rigidlytogether.
 10. A floating cover for inside a tank, comprising a pluralityof laterally spaced horizontal pontoons, a deck supported by thepontoons, at least some of said pontoons including longitudinally spacedaligned tubular members, a pair of brackets secured to the opposed endsof adjacent tubular members, each bracket having upper and lowerhorizontal flanges disposed in overlapping relation with the flanges ofthe other bracket, said flanges and deck having aligned verticalopenings therethrough, and a vertical sleeve mounted in said openingsand projecting above the deck and below the brackets, said cover alsoincluding a post extending through each sleeve and downwardly below it,and a removable cap mounted on the upper end of the sleeve, said postbeing removable upwardly through the sleeve when said cap is removed,whereby the post can be replaced by a post of a different length.